Android MediaPlayer 在屏幕关闭后继续播放

Question

I'm trying to follow the Core App Quality guideline FN-A1 that says that audio shouldn't play when the screen is off, so I checked it, and it does continue playing after I turn the screen off, but I'm not sure why. I don't think I'm using a service, and it seems that MediaPlayer should stop playing by default. Can anyone help me figure what I did wrong? I've copied the relevant parts of code. Thanks

public class RecordActivity extends BaseActivity {
MediaPlayer playback;

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_record);
        listView = (ListView)findViewById(R.id.listView);
        dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/" + getString(R.string.app_name));

        listView.setOnItemLongClickListener(new AdapterView.OnItemLongClickListener() {
        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long id) {
            String item = ((TextView) view).getText().toString();
            File itemFile = new File(dir + "/" + item + ".wav");
            if (itemFile.exists()) {
                playback = MediaPlayer.create(getApplicationContext(), Uri.fromFile(itemFile));
                try {
                    playback.start();
                } catch (NullPointerException e) {
                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(), R.string.errorFileNull, Toast.LENGTH_SHORT).show();
                }
            }
            else {
                Toast.makeText(getApplicationContext(), R.string.errorNotRecorded, Toast.LENGTH_SHORT).show();
            }
           return true;
        }
    });
    }
    }

Answer 1

You should stop the MediaPlayer in onPause:

if (playback != null && playback.isPlaying()) {
        playback.pause();
    }

Resume it in onResume:

if (playback != null && !playback .isPlaying()) {
                playback.start();
    }

Answer 2

Heads Up!

Notes About Media player

1. MediaPlayer is state oriented, and handling its errors is not as easy as it seems. If you need this in a reliable environment you have to consider setting an OnErrorListener at least

Notes About the code itself

1. You are catching a NullPointerException

// the better way is to check

if(playback == null){ 
    Toast.makeText(getApplicationContext(), R.string.errorFileNull, Toast.LENGTH_SHORT).show(); 
}